The present disclosure relates to an evaporated fuel processing device utilizing a flow rate control valve as a valve positioned in a passage connecting a fuel tank with a canister. The valve is maintained in a valve closed state when the stroke amount, representing the axially traveled distance of a movable valve part relative to a valve seat from an initial state of the valve, is less than or equal to a predetermined cutoff level, so as to allow the fuel tank to be maintained in a sealed state.
Japanese Laid-Open Patent Publication No. 2011-256778 discloses an evaporated fuel processing device equipped with the above-described flow rate control valve as a valve positioned in a passage connecting a fuel tank with a canister. A movable valve part of the flow rate control valve needs to be moved a predetermined amount in a valve-opening direction from an initial state of the valve, after a valve opening motion has started, in order to reach a valve opening start position where the valve is open to a degree where the fuel tank can communicate with the canister through the passage. The valve opening start position is learned in advance so that a normal valve opening control would start from the pre-learned valve opening start position in order to rapidly control the valve opening for flow rate control. For this learning to occur, the valve opening start position must be detected, where this detection of the opening start position is executed through detecting a reduction of the internal pressure of the fuel tank at said position.